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Erratum Regarding “Cystatin C in Prediction of Acute Kidney Injury: A Systematic Review and Meta-analysis” (Am J Kidney Dis 2011; 58:356-365)
Erratum Regarding “Cystatin C in Prediction of Acute Kidney Injury: A Systematic Review and Meta-analysis” (Am J Kidney Dis 2011; 58:356-365) The article entitled “Cystatin C in Prediction of Acute Kidney Injury: A Systematic Review and Metaanalysis” (Zhang et al, American Journal of Kidney Diseases 2011;58(3):356-365) contained important errors in analysis and presentation of data. In the article as published, the pooled area under the receiver operating characteristic curve (AUROC) was calculated using a fixed-effects model weighted by the inverse of the study variances; however, given the highly significant test for heterogeneity, use of a random effects model is more appropriate. In addition, analyses are listed for multiple measurement times for cystatin C in some studies. Because these measurements were performed in the same individuals, they do not constitute independent subgroups and therefore it is not appropriate to treat them as such in pooling the data. Moreover, the figures showing results were erroneously described as representing hierarchical summary ROC (HSROC) curves; in fact, they represent summary ROC (SROC) curves. Also, these figures plot a separate circle for each data set (ie, a set of measurements at a particular time point), but the analysis should have been based on one estimate for each study. When the key calculations of the article are repeated using methodology that corrects the errors detailed in the preceding, the overall conclusions of the article remain intact. Thus, sentences 2 to 7 of the results subsection of the abstract should be corrected from: Across all settings, the diagnostic OR for serum CysC level to predict AKI was 23.5 (95% CI, 14.2-38.9), with sensitivity and specificity of 0.84 and 0.82, respectively. The area under the receiver operating characteristic curve (AUROC) of serum CysC level to predict AKI was 0.96 (95% CI, 0.95-0.97). Subgroup analysis showed that serum CysC was of diagnostic value when measured early (within 24 hours after renal insult or intensive care unit admission). For the diagnostic value of urinary CysC excretion, the diagnostic OR was 2.60 (95% CI, 2.01-3.35), with sensitivity and specificity of 0.52 and 0.70, respectively. The AUROC of urinary CysC excretion to predict AKI was 0.64 (95% CI, 0.62-0.66).
to the following: Across all settings, the diagnostic OR for serum CysC level to predict AKI was 27.7 (95% CI, 12.8-59.8), with sensitivity and specificity of 0.86 and 0.82, respectively. The area under the receiver operating characteristic curve (AUROC) of serum CysC level to predict AKI was 0.87 (95% CI, 0.81-0.93). In an analysis excluding studies that did not clearly define the measurement time point, early serum CysC (within 24 hours after renal insult or intensive care unit admission) remained of diagnostic value. For the diagnostic value of urinary CysC excretion, the diagnostic OR was 3.10 (95% CI, 2.00-4.81), with sensitivity and specificity of 0.61 and 0.67, respectively. The AUROC of urinary CysC excretion to predict AKI was 0.67 (95% CI, 0.63-0.71).
Corrected versions of Figs 2-4 and Table 5 are provided as part of this erratum; also, the first row of Table 6 (diagnostic accuracy of serum CysC on admission for predicting AKI) should read 12.1 (8.0-18.4) for the diagnostic OR (95% CI); 81% (72%-88%) for sensitivity (95% CI); 74% (64%-82%) for specificity (95% CI), and 0.85 (0.79-0.91) for AUROC (95% CI). The following updates to the text are necessary to reflect the updated versions of Figs 2-4 and Table 5: 1. On page 361, second column, the second full sentence should read “Across all settings, we found a diagnostic OR of 27.7 (95% CI,12.8-59.8) for serum CysC level to predict AKI at a sensitivity and specificity of 0.86 and 0.82, respectively (Fig 2).” 2. On page 361, second column, the fourth full sentence should read “In an analysis excluding studies that did not clearly define the measurement time point, early serum CysC (within 24 hours after renal insult or intensive care unit admission) also was effective in predicting AKI, with diagnostic OR of 21.7 (95% CI, 10.2-46.2), sensitivity of 0.83, and specificity of 0.81 (Fig 3).” 3. On page 361, second column, the seventh full sentence should read “Areas under the curve (AUCs) were provided in all studies, and the pooled AUROC was 0.87 (95% CI, 0.81-0.93).” 4. The eighth sentence of the second column of page 361 should be omitted. 5. On page 362, second column, the last 2 sentences of the Results section should read “We combined data in 4 studies and found a diagnostic OR of 3.10 (95% CI, 2.00-4.81) for urinary CysC excretion to predict AKI at sensitivity and specificity of 0.61 and 0.67, respectively (Fig 4). The pooled AUROC was 0.67 (95% CI, 0.63-0.71) for urinary CysC excretion to predict AKI (Table 5).” The authors regret any confusion caused by these errors.
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Am J Kidney Dis. 2012;59(4):590-592
Erratum
Figure 2. Summary receiver operating characteristic (SROC) plot of serum cystatin C level to predict acute kidney injury across all settings. Based on combined sensitivity and specificity weighted for sample size of each study reflected by the size of the circles, showing average sensitivity and specificity estimate of the study results (open diamond) and 95% confidence region around it. The 95% prediction region represents the confidence region for a forecast of the true sensitivity and specificity in a future study. Heterogeneity is great, represented by the I2 of 94%.
Am J Kidney Dis. 2012;59(4):590-592
Figure 3. Summary receiver operating characteristic (SROC) plot of early (⬍24 hours) serum cystatin C level to predict acute kidney injury. Based on combined sensitivity and specificity weighted for sample size of each study reflected by the size of the circles, showing average sensitivity and specificity estimate of the study results (solid square) and 95% confidence region around it. The 95% prediction region represents the confidence region for a forecast of the true sensitivity and specificity in a future study. The heterogeneity is great, represented by the I2 of 92%.
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Erratum
Figure 4. Summary receiver operating characteristic (SROC) plot of urinary cystatin C excretion to predict acute kidney injury. Based on combined sensitivity and specificity weighted for sample size of each study reflected by the size of the circles, showing average sensitivity and specificity estimate of the study results (solid square) and 95% confidence region around it. The 95% prediction region represents the confidence region for a forecast of the true sensitivity and specificity in a future study. The heterogeneity is great, represented by the I2 of 98%.
Table 5. Pooled Diagnostic Accuracy of CysC in Various Settings
Setting (no. of studies)
AKI prediction using SCysC (9) AKI prediction using early SCysCb (7) AKI prediction using SCysC in adults (8) AKI prediction using UCysC (4)
Sensitivity (95% CI)
Specificity (95% CI)
DOR (95% CI)
AUROCa (95% CI)
I2 (%)
Positive Likelihood Ratio (95% CI)
Negative Likelihood Ratio (95% CI)
0.86 (0.77-0.92) 0.82 (0.74-0.88) 27.7 (12.8-59.8) 0.87 (0.81-0.93)
79
4.79 (3.16-7.26) 0.17 (0.10-0.29)
0.83 (0.74-0.89) 0.81 (0.70-0.89) 21.7 (10.2-46.2) 0.85 (0.77-0.93)
84
4.54 (2.73-7.55) 0.21 (0.14-0.32)
0.84 (0.74-0.90) 0.81 (0.72-0.89) 23.1 (10.4-51.2) 0.88 (0.82-0.94)
77
4.61 (2.88-7.37) 0.20 (0.12-0.33)
0.61 (0.36-0.81) 0.67 (0.51-0.80) 3.10 (2.00-4.81) 0.67 (0.63-0.71)
26
1.82 (1.58-2.10) 0.59 (0.39-0.89)
Abbreviations: AKI, acute kidney injury; AUROC, area under the receiver operating characteristic curve; CI, confidence interval; CysC, cystatin C; DOR, diagnostic odds ratio; SCysC, serum cystatin C; SE, standard error; UCysC, urinary cystatin C. a AUROC was estimated by using a random-effects model. b Early was defined as within 24 hours after admission or renal insult, and studies that did not clearly define the measurement times were excluded. 592
Am J Kidney Dis. 2012;59(4):590-592
to the following: Across all settings, the diagnostic OR for serum CysC level to predict AKI was 27.7 (95% CI, 12.8-59.8), with sensitivity and specificity of 0.86 and 0.82, respectively. The area under the receiver operating characteristic curve (AUROC) of serum CysC level to predict AKI was 0.87 (95% CI, 0.81-0.93). In an analysis excluding studies that did not clearly define the measurement time point, early serum CysC (within 24 hours after renal insult or intensive care unit admission) remained of diagnostic value. For the diagnostic value of urinary CysC excretion, the diagnostic OR was 3.10 (95% CI, 2.00-4.81), with sensitivity and specificity of 0.61 and 0.67, respectively. The AUROC of urinary CysC excretion to predict AKI was 0.67 (95% CI, 0.63-0.71).
Corrected versions of Figs 2-4 and Table 5 are provided as part of this erratum; also, the first row of Table 6 (diagnostic accuracy of serum CysC on admission for predicting AKI) should read 12.1 (8.0-18.4) for the diagnostic OR (95% CI); 81% (72%-88%) for sensitivity (95% CI); 74% (64%-82%) for specificity (95% CI), and 0.85 (0.79-0.91) for AUROC (95% CI). The following updates to the text are necessary to reflect the updated versions of Figs 2-4 and Table 5: 1. On page 361, second column, the second full sentence should read “Across all settings, we found a diagnostic OR of 27.7 (95% CI,12.8-59.8) for serum CysC level to predict AKI at a sensitivity and specificity of 0.86 and 0.82, respectively (Fig 2).” 2. On page 361, second column, the fourth full sentence should read “In an analysis excluding studies that did not clearly define the measurement time point, early serum CysC (within 24 hours after renal insult or intensive care unit admission) also was effective in predicting AKI, with diagnostic OR of 21.7 (95% CI, 10.2-46.2), sensitivity of 0.83, and specificity of 0.81 (Fig 3).” 3. On page 361, second column, the seventh full sentence should read “Areas under the curve (AUCs) were provided in all studies, and the pooled AUROC was 0.87 (95% CI, 0.81-0.93).” 4. The eighth sentence of the second column of page 361 should be omitted. 5. On page 362, second column, the last 2 sentences of the Results section should read “We combined data in 4 studies and found a diagnostic OR of 3.10 (95% CI, 2.00-4.81) for urinary CysC excretion to predict AKI at sensitivity and specificity of 0.61 and 0.67, respectively (Fig 4). The pooled AUROC was 0.67 (95% CI, 0.63-0.71) for urinary CysC excretion to predict AKI (Table 5).” The authors regret any confusion caused by these errors.
590
Am J Kidney Dis. 2012;59(4):590-592
Erratum
Figure 2. Summary receiver operating characteristic (SROC) plot of serum cystatin C level to predict acute kidney injury across all settings. Based on combined sensitivity and specificity weighted for sample size of each study reflected by the size of the circles, showing average sensitivity and specificity estimate of the study results (open diamond) and 95% confidence region around it. The 95% prediction region represents the confidence region for a forecast of the true sensitivity and specificity in a future study. Heterogeneity is great, represented by the I2 of 94%.
Am J Kidney Dis. 2012;59(4):590-592
Figure 3. Summary receiver operating characteristic (SROC) plot of early (⬍24 hours) serum cystatin C level to predict acute kidney injury. Based on combined sensitivity and specificity weighted for sample size of each study reflected by the size of the circles, showing average sensitivity and specificity estimate of the study results (solid square) and 95% confidence region around it. The 95% prediction region represents the confidence region for a forecast of the true sensitivity and specificity in a future study. The heterogeneity is great, represented by the I2 of 92%.
591
Erratum
Figure 4. Summary receiver operating characteristic (SROC) plot of urinary cystatin C excretion to predict acute kidney injury. Based on combined sensitivity and specificity weighted for sample size of each study reflected by the size of the circles, showing average sensitivity and specificity estimate of the study results (solid square) and 95% confidence region around it. The 95% prediction region represents the confidence region for a forecast of the true sensitivity and specificity in a future study. The heterogeneity is great, represented by the I2 of 98%.
Table 5. Pooled Diagnostic Accuracy of CysC in Various Settings
Setting (no. of studies)
AKI prediction using SCysC (9) AKI prediction using early SCysCb (7) AKI prediction using SCysC in adults (8) AKI prediction using UCysC (4)
Sensitivity (95% CI)
Specificity (95% CI)
DOR (95% CI)
AUROCa (95% CI)
I2 (%)
Positive Likelihood Ratio (95% CI)
Negative Likelihood Ratio (95% CI)
0.86 (0.77-0.92) 0.82 (0.74-0.88) 27.7 (12.8-59.8) 0.87 (0.81-0.93)
79
4.79 (3.16-7.26) 0.17 (0.10-0.29)
0.83 (0.74-0.89) 0.81 (0.70-0.89) 21.7 (10.2-46.2) 0.85 (0.77-0.93)
84
4.54 (2.73-7.55) 0.21 (0.14-0.32)
0.84 (0.74-0.90) 0.81 (0.72-0.89) 23.1 (10.4-51.2) 0.88 (0.82-0.94)
77
4.61 (2.88-7.37) 0.20 (0.12-0.33)
0.61 (0.36-0.81) 0.67 (0.51-0.80) 3.10 (2.00-4.81) 0.67 (0.63-0.71)
26
1.82 (1.58-2.10) 0.59 (0.39-0.89)
Abbreviations: AKI, acute kidney injury; AUROC, area under the receiver operating characteristic curve; CI, confidence interval; CysC, cystatin C; DOR, diagnostic odds ratio; SCysC, serum cystatin C; SE, standard error; UCysC, urinary cystatin C. a AUROC was estimated by using a random-effects model. b Early was defined as within 24 hours after admission or renal insult, and studies that did not clearly define the measurement times were excluded. 592
Am J Kidney Dis. 2012;59(4):590-592